The overall safety and performance of a vehicle is dependent, in part, on the plastic components used throughout the vehicle. Many people think that when it comes to cars, plastic parts are features like the dashboard, seats and floor mats. But thermoplastics are used in much more important places throughout a vehicle, many of them under the hood in the car’s powertrain and fuel systems.
In fact, of the approximately 30,000 parts in a vehicle, about 1/3 are made of plastic, with about 39 different types of basic plastics and polymers used. About 70% of the plastic used comes from four polymers: polypropylene (PP), polyurethane (PU), polyamide (PA), and polyvinyl chloride (PVC).1
There are significant benefits of using plastic when manufacturing vehicle components, and working with a custom injection molder experienced in the automotive industry is key to ensuring that the components — and the systems they are used in — are up to National Highway Traffic Safety Administration (NHTSA) and other strict standards.
A skilled injection molder will be able to select the plastics that have the best polymer science to deliver on the performance needs of a particular component, and to identify the production process and part geometry that take utmost advantage of the plastics in providing these features and benefits:
Safety / Crash Performance
Even with numerous innovations involving plastic automotive parts and designs in 2020, safety remains the #1 factor in the selection of engine and drivetrain components. An experienced injection molder will select polymers that have been proven highly effective in vehicle intrusion, crushing, and a wide range of other automotive testing. Innovation in plastics is robust and ongoing, with advancements in safety happening at a very fast rate.
Unlike most metals, plastic provides high rigidity with a low weight, and the ongoing development of new polymer types is allowing manufacturers to replace more heavy steel in vehicles every day. The development of new high-performance components with lower specific gravity will further reduce a vehicle’s weight and, as a result, improve its fuel efficiency. Plastic components also have the potential to improve the performance of onboard crash avoidance and performance systems.
Weather and Wear Resistance
Many plastics are able to withstand extreme weather conditions, such as intense sunlight UV rays, rapid temperature swings, and extreme dry and wet conditions — some of which make metal an impractical choice. Plastics can also withstand the significant wear presented by tough terrains.
Property Retention Over Service Temperature Range
The right plastics can maintain their integrity over a temperature range of -40° to +200°F without compromise in performance, making them ideal for under-the-hood applications.
Compared to metal, plastic part pricing is usually much lower because the injection molding process has faster cycle times. Also, plastic stock can be colored with color concentrates before molding, which eliminates the costly secondary operation of painting. Lastly, for assembly, a single injection-molded part (or one with snap-fit connections) eliminates welded joints and fasteners.
Compatibility With Mechanical Fasteners
Speaking of fasteners, plastics can work cohesively with metal connectors throughout the auto assembly; they also allow for tight tolerances and can be precisely molded to fit into tight spaces within the larger system. Plastic also contributes to the load-bearing strength of a component while providing the necessary elasticity.
While not a feature that directly benefits a vehicle, thermoplastic components also can be recycled. At the end of its life, a plastic part can be easily dismantled and converted into new uses.
With the correct plastic chosen by a custom injection molder with automotive molding expertise, it will deliver the safety and performance levels required by state and federal regulations and major auto manufacturers — not to mention benefits like lower cost, lighter weight/higher efficiency, and improved driver, passenger and pedestrian safety. Learn more about the benefits of using plastic parts in automotive applications by downloading our Guide to Designing for Complex Automotive Applications.
1Nexant, Plastics in the Automotive Industry – Which Materials Will Be the Winners and Losers?, February 27, 2019.